Telecommunication networks are moving towards an all-IP environment with unified protocols in both access and core networks. Moreover, the distinction between mobile and fixed environment is becoming less and less evident. The demand for broadband, multimedia-type type of services over the few next years will continue to grow and in time it is expected to compete with voice services not only in the traffic volume but also in the share of the service providers revenue.

Increased competition among numerous service providers and the need to differentiate themselves in the marketplace is resulting in the necessity to reduce the network cost, increase the overall efficiency, and introduce new broadband multimedia applications. It is believed that these goals can be best met by the integration of services, and their provision through the network based on a single transport mode.

Satellite communications are currently not keeping pace with the development witnessed in terrestrial networks, however in an all-IP environment they could easily facilitate early deployment of the service to many users currently out of the reach of communication services. Deployment of such an all-IP environment in the satellite segment, however, requires examination/study of suitability of the existing protocols and algorithms, and implementation of the required modifications/adaptations or even development of more efficient algorithms taking into account peculiarities of satellite systems.

With the demise and/or the continued financial problems of some current narrowband non-GEO constellations, understandably there has been some discouragement in the satellite telecommunications community. Such systems find it difficult to compete with globally deployed terrestrial mobile networks. On the other hand, there is a real demand for broadband applications coming from the market, and the deployment of the future satellite systems has to be driven by these new requirements, especially in areas and scenarios where terrestrial networks are not so well established or suited. Moreover, lessons learned during the last decade also push more interest again towards the appeal of GEO systems with their inherent broadcast and multicast features, may it be provision of regional or "nearly global" service, achieved by respective solutions ranging from one stand-alone GEO satellite over a regional GEO cluster to interconnected GEOs forming a simple ring or mesh network. In the non-GEO area, recently significant amount of the research work has been devoted to the implementation of the optical intersatellite links (ISLs) and to all-optical switching on-board of the satellite. The transition from electronic to optical technology will especially lead to an increase of channel capacity and to extremely fast processing and forwarding of information in a future space backbone.

Satellite communications are expected to play an important role in such competitive environment, driven by some recent technological advances which enabled (i) the implementation of efficient intersatellite links for the traffic interconnection in the satellite segment, (ii) onboard processing capabilities aiming to improve dynamic resource utilisation and flexibility, and (iii) multiple spot beam coverage to optimise bandwidth efficiency. Based on these advances, broadband satellite networks will represent an attractive solution to provide two way connectivity direct to the end user and to furnish new services such as high speed internet access and private network solutions. Furthermore, satellite networks are best suited to satisfy the increasing demand for the broadcast and multicast type of services with additional advantage of providing global accessibility.

The main objective of the Action is to contribute to the identification of key requirements, analysis, performance comparison, architectural design and protocol specification of future packet-oriented satellite communication systems, with a clear focus on Internet-type system concepts, applications and protocols/techniques on the various layers. In order to guarantee maximum benefit and flexibility, the Action must first of all assess the interesting satellite-specific market segments and potential at an early stage and come up with a clearly focussed set of reference scenarios (global/regional, GEO/non-GEO, broadcast/ multicast/interactive, QoS/best-effort, all-IP/hybrid, ...) as a basis for further R&D work that goes into the details of technical solutions. However, ongoing research will always have to monitor and evaluate ongoing activities in both the wireline and the (terrestrial) wireless Internet world and be open to required changes of the once identified working basis in the rapidly changing communications world. Such monitoring should cover newly deployed systems (like first and upgraded return channel systems) as well as more basic R&D work in both parallel COST, IST, and ESA programmes.